Orthogonal Frequency Division Multiplexing (OFDM) is one technique for multi-carrier digital modulation. OFDM is currently very popular and finding use in a wide variety of applications, including cellular communications, wireless networks, broadcasting, and the like.
In typical OFDM systems, a transmitter sends data at a certain rate, fTx. Similarly, a receiver samples the transmitted data at a certain rate, fRx. Ideally, the transmitter and receiver are accurately synchronized, thereby assuring that the frequencies of the sub-carriers remain orthogonal. Should the sub-carriers deviate in frequency such that orthogonality is lost, the system can experience cross-talk between the sub-carriers, otherwise known as Inter-Carrier Interference (ICI).
However, in real-world systems, some amount of frequency mismatch (also referred to as sampling frequency offset or “SFO”) is expected. Sources of frequency mismatch include, e.g., frequency offset between the transmitter and receiver oscillators and the Doppler shift from movement and multi-path fading. In order to correct for SFO, many systems measure SFO during transmission and perform functions, such as resampling, based on the measured SFO. However, currently available OFDM systems typically have some amount of error in SFO estimations, especially if fast time varying channels are considered. Currently there is no solution available that can decrease the SFO error in fast time varying channels while adding little extra complexity to existing systems.